GENERAL TECHNIC 443 



From a practical standpoint, therefore, to be suitable for use as 

 antigen in the syphilitic reaction any extract or preparation must fulfill 

 the following requirements: 



1. It should be largely free from anticomplementary action. 



2. It should likewise be free from hemolytic action, in small doses at 

 least. 



3. It should possess a high degree of sensitiveness for the syphilitic 

 antibody, i. e., be capable of absorbing relatively large -amounts of com- 

 plement in the presence of syphilitic serum. A good antigen is one that, 

 in small amounts, is perfectly antigenic, and that does not become 

 anticomplementary or hemolytic until from four to ten times this 

 amount is used. 



4. It should be quite stable and not difficult to prepare, and different 

 preparations should bear a certain relationship to one another in their 

 properties that is they should keep well, and different extracts prepared 

 in the same manner should show fairly constant antigenic, anticomple- 

 mentary, and hemolytic doses. 



Preparation of Antigens. The following antigens have been most 

 widely used and recommended: 



1. Aqueous extract of syphilitic livers. 



2. Alcoholic extracts of syphilitic liver. 



3. Alcoholic extracts of normal organs. 



4. Alcoholic extracts of normal organs reenforced with cholesterin. 



5. Acetone-insoluble lipoids. 



6. Lecithin and cholesterin. 



7. Aqueous extracts of pallidum culture. 



1. Aqueous Extracts of Syphilitic Livers. This is the original anti- 

 gen, as employed by Wassermann, Neisser, and Bruck; Wassermann still 

 uses these extracts in preference to others. They may contain spiro- 

 chetes or their direct derivatives, and, as shown originally by Wasser- 

 mann and Neisser, may be true biologic antigens, for when injected into 

 monkeys, antibodies are formed. 



No satisfactory analyses of these extracts have been made. Chem- 

 ically they differ in no essential respect from the liver of acute yellow 

 atrophy (Ehrmann and Stern; Seligman and Pinkus). As antigen they 

 are more efficient than similar, extracts of normal liver. The nature of 

 the specific factor has not yet been demonstrated with certainty. They 

 react with the serums of leprosy and yaws, and, as in the case of other 

 antigens, their main antigenic principle is apparently due to the presence 

 of lipoids. 



